Arylamine N-acetyltransferases (Nats) catalyze the acetylation of the extracyclic nitrogen of hydrazines and aromatic amines including the tobacco smoke carcinogen 4-aminobiphenyl (4AB). Two genes NAT I and NAT 2 each exhibit polymorphisms that result in variations in enzyme activities. Associations of NAT genes and susceptibility to smoking-related urinary bladder cancer have been reported. However, the involvement of one or both NAT genes, interactions between the two genes and genetic-environmental interactions are not fully understood. The overall goal is to investigate these relationships in genetically-defined mice. The hypothesis to be tested is that susceptibility to aromatic amine genotoxicity is associated with tissue specific expression of specific combinations of NAT I and NAT 2 genotypes. The specific aims are 1) to identify variants of mouse Nat 1; 2) to create a controllable knockout of Nat I and Nat 2; 3) to over-express Nat I and/or Nat 2 in a particular tissue using tissue specific promoters in transgenic mice; 4) to evaluate Nat 1 and Nat 2 expression in transgenic and knockout mice and 5) to detect 4AB-DNA adducts in mice genetically defined at Nat I and/or Nat 2. The controllable knockout without hepatic Nat genes will be achieved using the Cre-loxP system to knockout the gene then crossing the mice with the "floxed" knockout to albumin promoter Cre transgenic mice. Transgenic animals over-expressing either or both Nat genes will also be developed. An albumin promoter will allow targeting of over-expression to liver. Mice differing in Nat genes will be exposed to 4AB and DNA adducts measured in target and non-target tissue using a monoclonal antibody and immunohistochemistry. These studies will show whether 4AB genotoxicity is modulated by Nat expression. The results will provide insight into genetic regulation of susceptibility to a carcinogen found in tobacco smoke.